Apparatus for filtering slimes.



W. A. STEDMAN. APPARATUS FOR FILTERING SLIMES.

APPLIGATION FILED AUG. 1a, 1913.

1,100,267, Patefited June 16,1914.

3 SHEETS-SHEET 1.

Z WET/VESSES 7 IIVVENTOI? COLUMBIA PLANQGRAPH cm. WASHINGTON. D. c

W. A. STEDMAN.

APPARATUS FOR FILTERING sums.

AIPLIOATION FILED AUG. 13, 1913. 1 100 261 Patented June 16, 1914.

3 SHEETS-SHEET 2.

A A? A l "A3 I COLUMBIA PLANOHRAPH 60.. WASHINGTO D. c.

W. A. STEDMAN.

APPARATUS FOR FILTERING SLIMBS.

APPLICATION FILED AUG.13, 1913.

1,100,267. P11611161 June 16, 1914.

- 3 SHEETS-SHEET 3.

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WWW- INVENTOR/ COLUMBIA PLANOUIIAFH 50.,WAsHlNaTON. D. c.

WILLIAM ARMOR STEDMAN, OF WONDER,

PATENT VACUUM FILTER COMPANY, INC., A

NEVADA, ASSIGNOE TO THE BUTTERS CORPORATION OF NEVADA.

APPARATUS FOR FILTERING- SLIMES.

Specification of Letters Patent.

Patented June 1 6, 1914..

Application filed. August 13, 1913. Serial No. 784,497.

I '0 all whom, it may concern Be it known that 1, WILLIAM AR'MoR S'rnnnarz, a citizen of the United States, and a resident of Wonder, county of Churchill,

and State of Nevada, have invented new and useful Improvements in Apparatus for Filtering Slimes, of which the following is a specification.

The object of my invention is to shorten the time taken for a cycle of operation in the process of filtering valuable compounds, such as slimes, which result from the Well known cyanid process of treating ores.

Another object of my invention is to lower the cost of filter leaves while at the same time increasing their life and value.

In abstracting the values from slimes one of the most difficult and troublesome problems is to dislodge reliably and Within an economical time, the slime cake from the surface of the filter medium after the filtering process has been completed without injuring the filter surface of the leaf.

It has been the practice heretofore to dislodge slime cakes by air pressure placed on the interior of the leaves while suspended in the air, or this has been accomplished in some cases by water under pressure being passed through the filter medium in a direction reverse to that of the filtrate. It has been supposed heretofore that to dislodge the cake reliably and within an economical time, pressure was necessary whether of air, water or other fluid in the dislodging step, and special precaution has sometimes been taken to get a uniformly thick, cohesive and resistant cake deposit such that the fluid under pressure might dislodge it as an entirety and make it unnecessary to use additional means to dislodge the cake completely. By my process such uniformity of the cake is of no importance at all to the cake dislodgment, and consequently the filtering operation may be more economical.

If notable internal pressure is put on a leaf for cake-dislodgment purposes, a heavy filter medium is necessary and means must be provided to prevent distention or ballooning of the filter medium. Various means have been devised to this end, all of which have added to the difficulty of cake-dislodgment. As a matter of practice, too, it is found that all such means are a hindrance to proper and economical operation; further, they shorten the life of the leaves, but they have been regarded as indispen sable when former practicable methods of cake-dislodgment by internal pressure have been used. I

The efiiciency of the leaves heretofore used is low, first, because a considerable amount of the filtering surface of the medium is obstructed by the means used to prevent ballooning, such as strips down the sides; and second, because of stitching the media together or by bolting strips onto the outside of the leaf to prevent ballooning, comparatively large holes are made in the media. Also, these holes make the media more liable to rupture under internal pressure, thus shortening their life.

My invention utilizes the discovery of Charles Butters that pressure is unnecessary to reliable cake-dislodgment within an economical time, and that complete success can be attained by saturation of the entire area of the filter medium. It is found in practice that these cakes have unusual adhesion and cohesion, and that when a cake is formed on each side of a filter leaf they are not easily dislodged. Due to the great cohesion of the cake it is very important that the upper part, as well the other parts, of the filter medium be saturated in the dislodging step, as it is found that the adhesion of the cake to the medium is greatly lessened, and that the time for dislodgment is materially shortened thereby. This has not been attained in leaves lacking the Butters relief valve because they contained enough air to prevent water reaching the top part thereof even when admitted under pressure. This was true in spite of the fact that the leaf might be under vacuous conditions at the time the Water was first admitted.

The cake to be dislodged from a filter medium adheres more closely to the surface of the filter medium if there is any eXcess'of extern al over internal pressure. It is, there fore, desirable tohave the internal and external pressures equalized during the dislodging step, and I have devised means to thatend, which equalize such pressures by allowing communication between the external and the internal water. A leaf which embodies my invention cannot have internal pressure during the dislodging step. But such pressure is not necessary since the cake can be tion of the leaf shown in dislodged without it. It is understood that the water may reach all the leaves quickly the cake is dislodged while the leaf is submerged in wash water. This means that there will be considerable hydrostatic pressure on the outside of the leaf. It has been found by experiment that the difference in specific gravity of the more or less dirty tank wash water and the relatively clean cake-dislodging water would be suflicient to maintain a column of the relatively clean water inside the leaf several inches higher l l l l r l than the level of the tank wash water so that the relief valve and the inlet for the eake-dislodging water may be several inches above the surface of the tank wash water without producing greater pressure inside the leaf than the outside pressure on the leaf.

The above fact is useful in practice as it gives considerable latitude between the level of the tank wash water and that of the entrance to the relief valve and that of the funnel valve through which the dislodging water is supplied to the leaf, thus preventing the entrance of the tank wash water into the leaf, While at the same time preventing eXcess of internal pressure.

The above facts make it possible to completely saturate the entire filtering surfaces during the dislodging step because the air is permitted to escape through the relief valve. Also, as there is never any internal pressure, in my type of leaf, a lighter filter cloth may be employed and all means heretofore required to prevent ballooning dispensed with. Therefore, the filter surfaces may be smooth, being clear of all manner of bracing, stitching or other surface-roughening means which have heretofore been neces sary to prevent ballooning when other practicable methods of cake-dislodgment have been used, and consequently the cake is more easily dislodged.

Other advantages will be apparent from the following detailed description taken in connection with the accompanying dravings, in which Figure 1 shows a diagrammatic plan view of a general lay-out showing a clean water source and piping for supplying the water to the leaves; Fig. 2 is a side elevation of the devices shown in Fig. 1; Fig. 3 is a plan of a portion of a vat with several leaves therein; Fig. 4 is a view of a leaf embodying my invention; and Fig. 5 shows a see- Fig. 4.

In Fig. 1 are shown a plurality of vats 1 in which the leaves 2 are placed as shown in Fig. 3. These leaves are connected with the clean water source 3 by means of piping all, risers 7, pipe 5, pipes 32 and funnel on one side, and by means of the pipe 37, pipes 32 and funnels 35 on the other side. In each case the pipes 32 may discharge into funnels or other suitable means for conducting water into the leaves. In order that the pipe 5 is arranged along the top of the vats and is connected with the pipe 1 from the water supply 3 by means of risers 7. The interior of the leaves is connected with the *acuum-pump 10 through end members 16, members 6, sight-glasses 38, valve members 09 and pipe 33. The pipes l, 5 and 33 are suitably supported by any means, such as members 34L- fastened to the side of the vat. The pipe 37 may be supported by similar means. In pipe +t is placed valve 6 so that the water may be admitted to, or cut ofl from, the leaves. In the pipe 37 is the valve 10 by which the admission of water into the pipe 37, and therethrough into the leaves through funnels 35, may be controlled as hereinafter explained. The pump 10 is shown connected with the pipe 83 for the purpose of creating a vacuum within the leaves when desired.

hen it is desired to begin the filtering operation the valves 8 and 4.0 are Closed, the valve 9 is opened and the pump 10 started to decrease the pressure within the filler leaves, and thereby draw a filtrate through and form cakes on the surface of the filter media 19. When cakes of snilicient thickness have been formed, they may be treated in well. known ways with barren solution and then with wash water, and they are then ready to be dislodged. The valve S) may then be closed and the valve 8 opened, thereby permitting water to run into the leaves from the tank 3 through the piping risers 7, pipe 5, pipes 32 and funnels 30, thus dispelling the air through the valves 35. filling the leaves, saturating the filter media and thereby causing the cakes to drop within four or five minutes. The valve members 31 will have been removed from the funnels to allow the entrance of water into the leaves. The thick slime is then run out from the bottom of the vats into the runway 12, and thence to the slime-pit. The vats may be properly supported by any convenient means such as the pillars 13 and I-beams 14, as shown in Fig. 4c.

The valves 35 are of the type shown in the drawings, for reasons given hereinafter.

As shown in Fig. i, the leaf comprises a frame having members 15, 16, 17 and 15%. preferably of tubing. Over this frame is secured a filter medium 19 of canvas or other suitable material. Inside the filter-leaf is a fibrous filler 20 preferably of cocoa-mat, for holding the sides thereof apart when vaeuum is created within the leaf. This filler may be supported by any suitable means. as for instance, from the top frame member 18.

The lower frame member 15 is perforated or slotted along its upper side and is connected to a vacuum-pump 10, or other pressure-decreasing means through the righthand end member 16 and the connection (3,

which may be of rubber, or other suitable material, sight-glass 38, valve member 39 and the pipe 33. The filtrate is removed by means of the pump 10.

The left-hand frame member 17 is plugged by any suitable means such as a wooden plug, shown at 21 in Fig. l. The top frame member 18 is perforated or slotted along its lower side and to this member is attached a suitable relief valve 35. This member is also plugged as shown at 28. and is rigidly connected to the righthand end member to make a rigid frame structure. It is useful to be able to wash out the cocoa mat occasionally between filtering operations by admitting water from the tank 3 through valve 40, pipe 37, pipes 32 into the funnels 35, and for this purpose the relief valve is preferably arovided with a funnel. At the time that the water is admitted the valve member, such as a ball 2-36, removed from the funnel. It is not necessary that the relief valve be connected to the frame member, but this arrangement is preferred and it is so illustrated in the drawings. The pipe 22 connecting the valve to the leaf may be of any suitable length. The relief valve should be connected to the upper portion of the leaf in order to allow the escape of air.

As is clearly shown in Figs. 4 and 5, the leaf has its filter medium entirely open at the bottom. The function of this arrangement is to equalize the pressure between the internal water and the external water during the time that the cake is to be dislodged. 'lhe filter medium 19, in this case, is composed of two separate pieces of suitable material, such as canvas, and they are suspended by being clamped between the headers of the leaf. They hang down over the outside of the cocoa-mat and the frame members 15, 16, 17 and 18. They may be sewed along the sides as far as the bottom frame member and they then extend a suitable length below the bottom frame member 15. I have found in practice that an extension of six or eight inches below the bottom frame member gives good results. This eX- tension may be more or less and satisfactory results obtained. The flaps 11 may be sewed together at points a foot or so apart to prevent buckling. In this type of leaf the cocoa-mat 20 may be suitably supported either wholly from the upper frame mem ber 18 or from the upper frame member and the side members or from the header, or even from the filter medium. This forms no part of my invention, however, and any suitable means of supporting the cocoa-mat will be sufficient. It is, of course, necessary that in this. as well as all other types of leaf using the cocoa-mat, the cocoa-mat must be supported a sufficient distance above the perforations or slots in the lower frame member so as not to obstruct these passages and thereby prevent the drawing out of the filtrate.

In the particular form shown in Fig. i the leaf is provided with a funnel valve at each upper corner. lVhile these valves may be similar in structure they have different functions. The function of the valve at the right-hand corner is to admit water without pressure into the leaf for the purpose of dislodging the cake as heretofore described. The functions of the funnel valve at the left-hand corner are to allow water to be run through the leaf for occasionally washing out the cocoa-mat, or other filler, after the cake has been dislodged, and to permit air to escape while the leaf is being filled with water from the funnel at the opposite corner during the eake-dislodging step. The funnel valves at the right-hand corners of the leaves may be dispensed with and water for dislodging the cakes supplied through the members 6, if desired. There can be no internal pressure even under these circumstances because the filter medium is openable all. the way across its bottom so that as soon as the hydrostatic pressure within the leaf nearly equals the hydrostatic pressure outside the leaf, the flaps 11 of the filter medium below the frame member 15 will open so as to allow free communication between the exterior and the interior water, and thus the pressures will be equalized and kept equalized so long as the flaps remain open. This open bottom of the filter medium automatically closes if the external pressure becomes greater than the internal pressure, and this prevents entrance thereafter of external water into the leaf.

The operation of my device is as follows :The leaf is completely submerged in the slimes bath, care being taken not to al low slimes to enter the funnel valves. To prevent slimes entering the leaf through the open bottom before the vacuum is turned on, water may be run through the leaf at that time by admitting it through the funnels 35 and allowing it to discharge through the open bottom. After the leaves are completely submerged the water supply through the funnels 35 is cut ofi, the balls placed therein, and suction applied to the interior of the leaf by any means such as a vacuum pump 10. As soon as the vacuum is turned on, the flaps 11 at the bottom of the leaf as well as the valves 30 and 35 will close and seal. The filtrate is carried off by the pressure-decreasing means and the suction continued until a cake of proper thickness is deposited on the filter surface. This cake may then be variously treated with barren solution and wash water, the flaps 11 at the bottom of the leaf, as well as valves 30 and 85 remaining sealed throughout these operations. In order to dislodge the cakes, the filter leaves being submerged in wash water, the vacuum is turned off, the balls 31 are removed from the funnels 30 and water is ad mitted through pipes 32 and funnels 30 into the bottom frame member 15. As the water rises in the leaf, the air passes out through the relief valve 35 at the left-hand corner so that the water may rise to the top of the leaf and completely fill it and so saturate the entire surface of the filter media. At some point during this filling operation the flaps 11 at the bottom of the leaf will open and permit communication between the external and internal water thereby equalizing the external and internal pressures, and the cakes Will then be rapidly dislodged. The filter leaf may then, if desired, be washed out internally by admitting water through the funnel valves 35 at the left-hand corner and allowing it to discharge through the flaps at the bottom which will be open at this time.

Having described my invention, what 1 claim as new and desire to secure by Letters Patent, is

1. A filter medium for a suction filter leaf open across the bottom.

2. A filter medium for a suction filter leaf, consisting of a bag open across the bottom.

3. A filter medium for a suction filter leaf open across the bottom and so arranged as to be closed by suction.

4. A filter medium for a suction filter leaf, consisting of a bag open across the bottom and so arranged as to be closed by suction.

5. A suction filter leaf comprising a frame and filter media carried by said frame, said media being open across the bottom.

6. A suction filter leaf comprising a frame and filter media carried by said frame, said media being closed along the top and sides and open across the bottom.

7. A suction filter leaf comprising a frame and filter media cooperating with said frame, said media being open across the bottom.

8. A suction filter leaf comprising a frame, filter media being closed along the top and sides of said frame and having open flaps depend ing below said frame.

suction filter leaf comprising a frame. filter media carried by said frame, said media being open across the bottom and so arranged as to be closed by suction.

10. A suction filter leaf comprising a frame. filter media carried by said frame. said media being closed along the top and sides and open across the bottom and being so arranged as to be closed across the bottom by suction.

11. A suction filter leaf comprising a frame, filter media cooperating with said frame, said media being open across the bottom and so arranged as to be closed by suction.

12. A filter leaf comprising a frame, filter media surrounding said frame, said media being closed along the top and sides of said frame and having open [laps depending below said frame, said flaps being so arranged as to be closed by suction.

In testimony whereof, I have signed my name to this specification, in the presence of two subscribing witnesses.

W'IlJLIAh I ARMOR STEDMAN.

lVitnesses Ron'r. G. Davms, W. H. MANNING.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. 0.

media surrounding said frame, said 

